What was a negative outcome of the Crusades?

In order to answer this question, we really need to first decide from whose perspective we are viewing the Crusades. What might be construed as positive for some (e.g., the capture of Jerusalem by the Crusaders in the First Crusade) could equally be seen as extremely damaging for others (e.g., the many Saracen soldiers who were killed in the process; the people who lived there who did not escape the worst of the fighting). Overall, indeed, it is arguable that the Crusades had far more negative effects than positive ones upon both sides. Even if we consider the First Crusade—ultimately, a military success for the Crusaders—"victories" such as the capture of Antioch first necessitated several long sieges which killed thousands, with members of both armies (and many civilians) dying of disease as well as in battle. This is before we even turn our attention to other subsequent crusades, such as the Second Crusade, in which Jerusalem was lost to the Saracens, or the Fourth Crusade, in which the Crusaders—content to ransack Constantinople for its riches—didn't get anywhere near Jerusalem.
The negative effects of the Crusades and Crusade-fervor were felt all across Europe, as well as in the Holy Lands. Crusading stirred up religious tensions and resulted in the slaughter of many Jews, with more than one crusader Pope suggesting that murdering Jews on the way to the Holy Lands was actually to be encouraged. Other sects, such as the Albigensians and the Cathars in southern France, fell victim to religious dissent and were massacred. This is not even to count the many Crusaders who were killed before they could return home. Overall, the Crusades resulted in very little benefit to the European countries who embarked upon them so fervently, with the exception of some monetary gain.